Active and passive smart materials

Smart materials can be termed as active or passive. Active materials posses the capacity to modify their material and geometric properties under application of electrical, thermal or magnetic field and thereby acquiring an inherent capacity to transduce energy. Piezoelectric materials, shape memory alloys, electro-rheological fluids and magnetostrictive materials are important active smart materials and they may be used as sensors and actuators [Figure 4.2]. Passive smart materials do not have the inherent capability to transduce energy. Fiber optic materials are good examples of passive smart material. They are mainly used for sensing purposes.

Figure 4.2 Some applications of smart materials: (clockwise) (a) Terfenol-D products
(b) SMA Catheter (c) PVDF film and (d) PZT actuator [ETREMA Products Inc.
and Sumitomo Metals (SMI) Electronic Devices Inc.]